linux-kernel - Re: [PATCH] sched: rt: Optimization function 'pick_next_rt

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Date:   Wed, 05 Apr 2023 16:04:38 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Li zeming <zeming@...china.com>, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: rt: Optimization function 'pick_next_rt_entity'

On Thu, 2023-04-06 at 07:29 +0800, Li zeming wrote:
> The moral of this function is to obtain the next RT scheduling entity
> object,while 'list_entry' Implementation function of  'container_of'
> returns the next RT scheduling entity object (no new code should be
> added afterwards), directly returning 'list_entry' The execution result
> is sufficient.

Suggest changing the subject from "Optimization function 'pick_next_rt_entity'
to "Simplify pick_next_rt_entity()"

Suggest simplifying the comment:

Remove useless intermediate variable "next" and its initialization.  Directly return the
next RT scheduling entity obtained from list_entry().

Otherwise the patch itself looks fine.

Reviewed-by: Tim Chen <tim.c.chen@...ux.intel.com>
> 
> Signed-off-by: Li zeming <zeming@...china.com>
> ---
>  kernel/sched/rt.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 0a11f44adee5..e9b1c08c20a7 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1769,7 +1769,6 @@ static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool f
>  static struct sched_rt_entity *pick_next_rt_entity(struct rt_rq *rt_rq)
>  {
>  	struct rt_prio_array *array = &rt_rq->active;
> -	struct sched_rt_entity *next = NULL;
>  	struct list_head *queue;
>  	int idx;
>  
> @@ -1779,9 +1778,8 @@ static struct sched_rt_entity *pick_next_rt_entity(struct rt_rq *rt_rq)
>  	queue = array->queue + idx;
>  	if (SCHED_WARN_ON(list_empty(queue)))
>  		return NULL;
> -	next = list_entry(queue->next, struct sched_rt_entity, run_list);
>  
> -	return next;
> +	return list_entry(queue->next, struct sched_rt_entity, run_list);
>  }
>  
>  static struct task_struct *_pick_next_task_rt(struct rq *rq)